I have to do some tests before i can tell a bit more. Look at this [tutorial] ([Release] + [Tutorial] Add new tattoos and overlays (Example Included)) to see how it works.
Maybe new clothes can be added via streaming.
Basically, we need to stream ydd-ytd-whatever and write special meta files. Then set them up in __resource.lua like a data files.
Then in game - just pick right drawable variation.